1. Field of the Invention
The present invention relates to a pump or pumping assembly, arrangement or combination; and more particularly relates to a new technique for providing axial thrust in such a pump or pumping assembly, arrangement or combination, e.g., including a vertical double-suction pump.
2. Brief Description of Related Art
Single-suction type impellers produce hydraulic thrust loads in the direction along their axis of rotation. In a vertically suspended pump, these axial thrust loads are transmitted from the impeller(s) at the bottom of the pump rotor assembly, through the shaft of the pump, and absorbed by a thrust bearing in the motor at the top of the pump. Axial thrust loads are beneficial in vertical pumps for two reasons:                1) Axial thrust loads applied to pump shafts in tension increase the rotor dynamic stiffness of the rotor system.        2) Axial thrust loads applied to pump shafts improve the internal alignment of the pump rotating elements to stationary elements.        
Typical double-suction type impellers produce no axial thrust loads from hydraulic forces; because their symmetrical geometry about the centerline of the impeller has the same pressure acting on both shrouds. Therefore, when typical double-suction impellers are used in vertically suspended pumps, the benefits of axial thrust loads pump shafts are not realized, and these types of pumps suffer from poor reliability.
In view of the aforementioned, there is a long felt need in the industrial pump industry for an improved design or technique that solves the problems related to realizing axial thrust loads in an industrial pump or pumping assembly, arrangement or combination, including a vertical double-suction pump.